Art of producing alumina.



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MAURICE BARNETT nun LGUl-IS TE'UEGEQEJ, 3F .LTEW YOAQK, Y.

ART OF PRODUCING ilLUlrifi l'lrL No Drawing.

T 0 all whom it may concern Be it known that we, MAURICE BARNETT andLOUIS BURGESS. citizens of the United States, residing at New York, inthe county of New York and State of New York, have invented ordiscovered certain new and useful Improvements in the Art of ProducingAlumina, of which the following is a specification.

This invention relates to the art of manufacturing alumina (aluminumoxid, A1 9 and has for its' object the production of alumina of a gradeadapted to be employed.

in the manufacture of metallic aluminum.

Instead of bauxite, heretofore commonly r L0 15.86% Fe 3 289 2 FeO -I54% SO. m. 30.9l%

The next step aims at the separation of the iron and this can beaccomplish-ed by following the procedure set forth in our applicationfor an improvement in the art of producing sulfate of alumina, filedDecember 18, 1916, Serial No. 137,713. In general this procedureconsists in the oxidation of the iron by means of ozone or ozonated airand the precipitation of the bulk of the iron by adding powderedcarbonate of lime to the solution, the carbonate of lime being addedslowly and the solution being constantly stirred during the addition ofthe precipitant. This operation is carried on until about 85% of theiron in solution has been precipitated as hydroxid when the precipitatemay be removed by filtration.

After the iron hydroxid has been filtered oh the filtrate is treatedwith a solution of caustic soda which will precipitate the remainingiron as hydroxid. This precipitate of iron hydroxid maythen, be filtereded and the resulting filtrate, which will consist Specification ofLetters Patent.

Patented Jan. g, 1918.

Application filed December 18, 1916. Serial No. 137,715.

of a pure solution of aluminum sulfate, may 55 be evaporated until theboiling point of the solution is just short of 120 degree centi grade.

' A solution of aluminum sulfate, boiling at a temperature just below120 0., contains twelve molecules of Water of crystallization,

which water of crystallization can be driven off by heating the aluminumsulfate a receptacle in which it is vigorously stirred while beingheated, this stirring or agitation serving to break up any aluminumsulfatdthat tends to cake and adhere to the sides or bottom of the ot orreceptacle when the material is heated.

From this receptacle the anhydrous all nun; sulfate is run into acalciner and h ed to temperature of approximately to, to v 50centigrade, the calcination being preferably carried out-in a furnace ofthe central flue type, in which the products of i5 combustion do notcome in contact with the vmateriat tube calcined. :Under the action ofthe heat the sulfuric acid, excepting a slight trace, is driven oil,;.apractically pure alumina, suitable for-electrolytic reduction,remaining.

. cost of producing the alumina in accordance our present invention ordiscovery may be reduced somewhat by utilizing the sulfuric acid whichis driven ofl in $5 the calcining operation. This passes over as sulfurdiozid (S0 and sulfur trioxid (S0 which may be converted back again intosulfuric acid by the well-known contact process.

thus described our inventiodor discovery we claim and desire to secureby Letters Patent:

1. The herein described process of proally pure alumina, consisting inevanc a solution of aluminum sulfate until the boiling point of thesolution is just below 120 0., thensut ijcting such condensed solutionto -the"ation of heat while being agitated, thus producing 100 anhydrousaluminum sulfate, andthen calcining the said fanhydrous sulfate at atemperature of approximately 550 to 650 C. in a suitable furnace. iv l2. The herein described process of producing substantially pure aluminaconsisting in evaporating asolution of. aluminum sulfate until theboiling point of the solution t 33:26 G. $11311 suhjecfing such ihzaaction 0% heat agitated thus prmiucinganhy 3, hen subgiwiing the Miterta *9 of approximaiieiy 550 to 650 313 gamma, thus drivin ofi, in agnsemls smteg. like sulfur cnntaine in the aluminum suifate, andzffigen.,a agcavcyr' sulfur as sulfurlc acul I In testlmany whereof 'Wefifiz0111:

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